1. Field
The present invention relates to an organic light emitting display device (OLED) and, more particularly, to an OLED including a green emission layer whose life span is improved.
2. Description of the Related Technology
An OLED includes an anode, a cathode, and an organic layer including an emission layer disposed between the anode and the cathode. The OLED is an emissive display which applies a voltage to the two electrodes so as to supply holes and electrons into the emission layer, and emits light by recombination of the holes and electrons supplied to the emission layer. Accordingly, the OLED does not need a backlight like an LCD, and thus can be made light and thin. Also, the OLED has attracted attention as a next generation display because it has low-voltage drivability, high luminous efficiency, wide viewing angle, and fast response speed, thereby realizing a high-quality moving picture. Such an OLED can realize full-color by forming a plurality of sub-pixels therein including red, green and blue emission layers. The emission layer may be formed of only a host material or a dopant. However, this configuration is not preferable because efficiency and brightness of the emission layer are very low, and an excimer property and the original property simultaneously occur owing to a self-packing phenomenon between molecules. Thus, the emission layer may be formed by doping a host material with a dopant.
As for a green emission material, the host material may be tri(8-hydroxyquinolinato)aluminum (hereinafter abbreviated as “Alq3”) or a stilbene derivative. The organic emission layer may be formed by doping the host material with a quinacridone derivative. In the case of using Alq3, interaction between molecules is so great that it causes cohesion between the molecules, thereby decreasing stability of the device. In the case of using the stilbene derivative, its efficiency is excellent but its thermal stability and thin film property are not, which again decreases the stability of the device. As a result, the device may have a short lifespan.